A load cell is a transducer that can convert a mechanical input to an electrical output. Some load cells include one or more strain sensors, which are typically made of a metal foil pattern or similar material. These strain sensors can be placed in such a way that the strain being measured will cause the metal foil pattern to flex. Depending on the direction of flexing, the metal foil pattern can be subjected to compressive or tensile forces. When the metal foil pattern is compressed, the length of the metal foil pattern is slightly reduced and the thickness is slightly increased, which results in an overall reduction in electrical resistance. When the metal foil pattern is under tensile stress, the length of the metal foil pattern increases slightly and the thickness is slightly reduced, resulting in an increase in electrical resistance. These small changes in electrical resistance can be detected and correlated to the strain experienced by the strain sensor.
The strain sensors of a load cell can be adhered to a variety of substrates, such as polyimide film, polyester film, ceramic, glass, silicon, and so on. Both sides of the substrate can be patterned so that flexing of the substrate produces compression on one side and tension on the other side. In some examples, the metal foil patterns on each side can be connected in a Wheatstone bridge to produce an output voltage that indicates both the magnitude and direction of the bending stress that the sensor, and the object to which the sensor is affixed, is experiencing.
The figures depict several examples of the presently disclosed technology. However, it should be understood that the present technology is not limited to the examples depicted.